1. Field of Invention
This invention relates to shift control methods/systems for at least partially automated vehicular mechanical transmission systems including various shift control techniques, such as control techniques wherein the desirability and/or probability of successfully completing a selected upshift are evaluated in view of existing vehicle operating conditions, which are based, at least in part, on determining and/or predicting the driving torque available at the vehicle drivewheels. In particular, the present invention relates to an adaptive shift control method/system for a fully or partially automated vehicular mechanical transmission system of the type shifting without disengagement of the vehicular master clutch which will determine a value indicative of vehicle drivewheel torque and will use this value as a transmission system control parameter.
More particularly, the present invention relates to an adaptive shift control for vehicular automated mechanical transmission systems which will continuously update the value of the control parameter indicative of engine flywheel torque, from which value and certain drivetrain characteristics, such as engaged gear ratio, tire size, efficiency, etc., drivewheel torque may be accurately determined. For automated or partially automated mechanical transmission systems, it is desirable to know the torque at the flywheel for many control algorithms. Knowing true torque at the flywheel will allow more precise shift control and makes possible advanced algorithms, such as shiftability and GCW calculations. The control system/method of the present invention uses torque information from the engine (preferably an electronic engine), along with vehicle and engine acceleration information, to determine this parameter.
2. Description of the Prior Art
Fully automatic and semi-automatic vehicular mechanical transmission systems utilizing electronic control units, usually microprocessor-based, are known in the prior art. Examples of such automated mechanical transmission systems may be seen by reference to U.S. Pat. Nos. 3,961,546; 4,361,060; 4,425,620; 4,631,679 and 4,648,290, the disclosures of which are incorporated herein by reference.
Another type of partially automated vehicular transmission system utilizes an automatic or semi-automatic shift implementation system/method for a mechanical transmission system for use in vehicles having a manually only controlled master clutch. The system usually has at least one mode of operation wherein the shifts to be automatically or semi-automatically implemented are automatically preselected. An electronic control unit (ECU) is provided for receiving input signals indicative of transmission input and output shaft speeds and/or engine speed and for processing same in accordance with predetermined logic rules to determine (i) if synchronous conditions exist, and (ii) in the automatic preselection mode, if an upshift or downshift from the currently engaged ratio is required and to issue command output signals to a transmission actuator and/or an engine fuel controller for shifting the transmission in accordance with the command output signals.
Transmission systems of this general type may be seen by reference to U.S. Pat. Nos. 5,050,079; 5,053,959; 5,053,961; 5,053,962; 5,063,511; 5,081,588; 5,089,962; 5,089,965 and 5,272,939, the disclosures of which are incorporated herein by reference.
While the above-described automatic and/or partially automatic shift implementation type vehicular mechanical transmission systems are well suited for their intended applications, they are not totally satisfactory as they will occasionally initiate an attempted shift, which, due to vehicle operating conditions, should not be permitted and/or cannot be completed. This is especially a concern for upshifts of a vehicle heavily loaded and/or traveling up a grade and/or for those automated mechanical transmission systems not provided with an automated clutch actuator and/or an input shaft brake and thus have input shaft deceleration limited to the normal or engine brake-assisted decay rate of the engine.
In accordance with the inventions of aforementioned co-pending U.S. Ser. No. 08/179,060 and U.S. Pat. No. 5,272,939, and of U.S. Pat. Nos. 5,133,229; 5,172,609 and 5,231,582, the disclosures of which are incorporated herein by reference, the above-discussed drawbacks of the prior art are minimized or overcome by the provision of shift control methods/systems for vehicular at least partially automated mechanical transmission systems which, upon sensing an automatic or manual selection of an upshift from a currently engaged gear ratio into a target gear ratio will, based upon currently sensed vehicle operating conditions, determine if the selected upshift is feasible (i.e., desirable and/or probably completible) and only initiate feasible shifts.
If the proposed upshift is not feasible, the shift request may be modified (i.e., a skip shift request changed to single shift) or cancelled for a predetermined period of time (such as 10 seconds).
The foregoing prior art control logic was not totally satisfactory, as the control parameter value indicative of drivewheel torque required expensive shaft torque sensors to acquire and/or was derived from gross engine torque values which do not account for torque losses due to vehicle assembler-installed accessories (such as air-conditioning, alternator, etc.) and for accelerating the engine, For example, during acceleration in the low gears of a heavy truck, the torque number reported from the engine on an SAE J1939-type datalink is a fairly high number at wide-open throttle. However, most of the torque the engine "says" it is producing is going to accelerate the engine rotating inertia and only a portion of that reported torque is going from the flywheel through the clutch to actually move the vehicle.